The movie had its moments, and the end had me crying. But the book allowed for so much more room to develop the characters, and the voice of the characters. There was a lot more self loathing for both Dex and Em in the book, that didn't come across very well in the movie. I normally find Anne Hathaway annoying, but she was a good Emma.
The movie was slow paced and dragged in the middle. I guess a book rich with detail and witty banter is going to be hard to adpapt?